Socket 462, AKA Socket A, is pretty much obsolete. No, your motherboard does not support pci-express (you linked to the processor twice, but a Socket A mobo won't have pci-express).
that used athlon xp processor (which isn't even for sale) is pretty much the same price as a socket 939 3000+ processor. i highly recommend you upgrade to at least socket 939. you'd just have to get a new motherboard, which are also quite cheap. if your current system is using ddr ram, then you can even carry over the ram you're using...
"Is virtue a thing remote? I wish to be virtuous, and lo! Virtue is at hand." -Confucius